Background Inotuzumab ozogamicin, an anti-CD22 antibody conjugated to calicheamicin, is active in acute lymphoblastic leukemia. Methods In this phase 3 trial, adults with relapsed/refractory acute lymphoblastic leukemia were randomized to inotuzumab ozogamicin or standard intensive chemotherapy. Primary endpoints were complete remission and overall survival. Results Primary intent-to-treat (ITT) analysis of complete remission included the first 218 (inotuzumab ozogamicin, n=109; standard, n=109) of 326 patients randomized. Complete remission rate was significantly better with inotuzumab ozogamicin (80.7% [95% CI, 72%–88%] vs 29.4% [21%–39%]; P<0.001), as was minimal residual disease (MRD)-negativity among responders (78.4% [68%–87%] vs 28.1% [14%–47%]; P<0.001); remission duration was longer (median, 4.6 [3.9–5.4] vs 3.1 [1.4–4.9] months; hazard ratio=0.55 [0.31–0.96], P=0.034). More patients proceeded to transplant with inotuzumab ozogamicin (41%) versus standard (11%; P<0.001). In the ITT survival analysis (n=326), progression-free survival was significantly longer with inotuzumab ozogamicin vs standard (HR, 0.45 [97.5% CI, 0.34–0.61]; P<0.001; median, 5.0 [95% CI, 3.7–5.6] vs 1.8 [1.5–2.2] months). The overall survival HR was 0.77 (97.5% CI, 0.58–1.03); P=0.04; median was 7.7 (95% CI, 6.0–9.2) vs 6.7 (4.9–8.3) months. 2-year overall survival rate was 23% (95% CI, 16%–30%) vs 10% (5%–16%). In the safety population, the most frequent nonhematologic inotuzumab ozogamicin treatment-emergent grade ≥3 adverse events were liver-related. Any grade veno-occlusive liver disease occurred in 15 (11%) patients receiving inotuzumab ozogamicin. Conclusion Patients receiving inotuzumab ozogamicin versus standard care achieved higher response, MRD-negativity rates, and prolonged progression-free survival and overall survival. Veno-occlusive disease was a major non-hematologic toxicity.

Using a laser-induced endothelial injury model, we examined thrombus formation in the microcirculation of wild-type and genetically altered mice by real-time in vivo microscopy to analyze this complex physiologic process in a system that includes the vessel wall, the presence of flowing blood, and the absence of anticoagulants. We observe P-selectin expression, tissue factor accumulation, and fibrin generation after platelet localization in the developing thrombus in arterioles of wild-type mice. However, mice lacking P-selectin glycoprotein ligand 1 (PSGL-1) or P-selectin, or wild-type mice infused with blocking P-selectin antibodies, developed platelet thrombi containing minimal tissue factor and fibrin. To explore the delivery of tissue factor into a developing thrombus, we identified monocyte-derived microparticles in human platelet–poor plasma that express tissue factor, PSGL-1, and CD14. Fluorescently labeled mouse microparticles infused into a recipient mouse localized within the developing thrombus, indicating that one pathway for the initiation of blood coagulation in vivo involves the accumulation of tissue factor– and PSGL-1–containing microparticles in the platelet thrombus expressing P-selectin. These monocyte-derived microparticles bind to activated platelets in an interaction mediated by platelet P-selectin and microparticle PSGL-1. We propose that PSGL-1 plays a role in blood coagulation in addition to its known role in leukocyte trafficking.

Background Inotuzumab ozogamicin (InO) is an antibody‐drug conjugate used for adults with relapsed/refractory B‐cell precursor (BCP) acute lymphoblastic leukemia (ALL). The INotuzumab Ozogamicin trial to inVestigAte Tolerability and Efficacy (INO‐VATE) previously reported improved outcomes with InO versus standard‐of‐care (SoC) chemotherapy. This article reports the final INO‐VATE results (≥2 years of follow‐up) and additional analyses of patient characteristics associated with improved outcomes. Methods Between August 27, 2012, and January 4, 2015, this multicenter, parallel, open‐label, phase 3 trial randomized 326 adults with relapsed/refractory ALL to InO (n = 164) or SoC (n = 162); 307 received 1 or more doses of the study drug (164 in the InO arm and 143 in the SoC arm). Results The complete remission (CR)/complete remission with incomplete hematologic recovery (CRi) rate was higher with InO versus SoC (73.8% vs 30.9%; 1‐sided P < .0001), with consistent CR/CRi rates across patient subgroups. The median overall survival (OS) was 7.7 months with InO and 6.2 months with SoC, with 2‐year OS rates of 22.8% and 10.0%, respectively (overall hazard ratio, 0.75; 97.5% confidence interval [CI], 0.57‐0.99; 1‐sided P = .0105). The predictors of OS with InO were the best minimal residual disease status, baseline platelet count, duration of first remission, achievement of CR/CRi, and follow‐up hematopoietic stem cell transplantation (HSCT; all 2‐sided P values < .05). More InO arm patients proceeded directly to HSCT after achieving CR/CRi before any follow‐up induction therapy (39.6% [95% CI, 32.1%‐47.6%] vs 10.5% [6.2%‐16.3%]; 1‐sided P < .0001). The most frequent all‐grade and grade 3 or higher adverse events in both arms were hematologic. Veno‐occlusive disease (VOD)/sinusoidal obstruction syndrome (SOS) was more frequent with InO (23 of 164 [14.0%] vs 3 of 143 [2.1%]). Conclusions In patients with relapsed/refractory BCP ALL in INO‐VATE, InO was associated with a greater likelihood of CR/CRi across key patient subgroups, and it served as a bridge to HSCT. Potential VOD/SOS risk factors must be considered when InO treatment decisions are being made.

PURPOSE Inotuzumab ozogamicin (CMC-544) is an antibody-targeted chemotherapy agent composed of a humanized anti-CD22 antibody conjugated to calicheamicin, a potent cytotoxic agent. This was a phase I study to determine the maximum-tolerated dose (MTD), safety, and preliminary efficacy of inotuzumab ozogamicin in an expanded MTD cohort of patients with relapsed or refractory CD22(+) B-cell non-Hodgkin's lymphoma (NHL). PATIENTS AND METHODS Inotuzumab ozogamicin was administered intravenously as a single agent once every 3 or 4 weeks at doses ranging from 0.4 to 2.4 mg/m(2). Outcomes included MTD, safety, pharmacokinetics, response, progression-free survival (PFS), and overall survival. Results Seventy-nine patients were enrolled. The MTD was determined to be 1.8 mg/m(2). Common adverse events at the MTD were thrombocytopenia (90%), asthenia (67%), and nausea and neutropenia (51% each). The objective response rate at the end of treatment was 39% for the 79 enrolled patients, 68% for all patients with follicular NHL treated at the MTD, and 15% for all patients with diffuse large B-cell lymphoma treated at the MTD. Median PFS was 317 days (approximately 10.4 months) and 49 days for patients with follicular NHL and diffuse large B-cell lymphoma, respectively. CONCLUSION Inotuzumab ozogamicin has demonstrated efficacy against CD22(+) B-cell NHL, with reversible thrombocytopenia as the main toxicity.

Thrombin, a central mediator of hemostasis and thrombosis, converts fibrinogen to fibrin and is a potent platelet activator. Activated platelets provide a surface for assembly of the tenase and prothrombinase complexes required for thrombin generation. The role of thrombin-induced platelet activation in platelet accumulation and its interplay with fibrin deposition during thrombus assembly has not been fully defined. We studied these processes during laser-induced thrombus formation by using real-time digital fluorescence microscopy in mice lacking protease-activated receptor-4 (Par4), which is necessary for thrombin responsiveness in mouse platelets. Juxtamural platelet accumulation immediately after laser injury was not different in wild-type and Par4 ؊/؊ mice. However, subsequent growth of platelet thrombi was markedly diminished in Par4 ؊/؊ mice. At the time of maximal thrombus size in wild type, platelet accumulation was more than 10-fold higher in wild type than in Par4 ؊/؊ mice. P-selectin expression, a marker of platelet activation, was reduced and delayed in Par4 ؊/؊ thrombi. In contrast to platelet activation and accumulation, the rate and amount of fibrin deposition, predominantly intramural and juxtamural in this model, were indistinguishable in Par4 ؊/؊ and wild-type mice. These results suggest that platelet activation by thrombin is necessary for normal propagation of a platelet thrombus at a distance from the injured vessel wall and hence for normal thrombus growth. However, platelet activation by thrombin is unnecessary for initial and limited accumulation of platelets at or near the vessel wall, and this limited accumulation of platelets and/or platelet-independent mechanism(s) of thrombin generation are sufficient for normal fibrin deposition in this model. blood coagulation ͉ intravital microscopy ͉ P-selectin